A heat pump may be configured to heat a vehicle's passenger cabin at low ambient temperatures and cool the vehicle's passenger cabin at higher ambient temperatures. The heat pump may transition from a heating mode to a cooling mode in response to driver input, or in response to automated controller commands that are based on ambient and/or passenger cabin environmental conditions. The heat pump may be transitioned between heating and cooling modes by changing a path that refrigerant flows within the heat pump. Additionally, the heat pump may be controlled responsive to different inputs during different operating modes. As a result, it may be possible for heat pump control signals to change significantly when the heat pump is switched from operating in a heating mode to operating in a cooling mode, or vice-versa. The change in heat pump control signals may be objectionable to vehicle occupants or it may increase degradation of heat pump components. Therefore, it may be desirable to provide a system and method that allows a heat pump to transitions between operating modes in a seamless way.
The inventors herein have recognized the above-mentioned disadvantages and have developed a heat pump method, comprising: commanding a compressor to provide a desired evaporator temperature in response to output of an evaporator temperature controller and output of a refrigerant pressure controller in a first heat pump operating mode; and commanding the compressor to provide a desired heater core temperature in response to output of a heater core temperature controller and output of the refrigerant pressure controller in a second heat pump operating mode.
By combining outputs of two controllers in one mode and two different controllers in a second mode, it may be possible to provide the technical result of providing a bumpless or seamless change in heat pump operation during a heat pump mode change. In one example, output of two controllers is adjusted based on output of at least one different controller so that controllers outputting commands for a control mode being entered are adjusted to command values that maintain a compressor command before and after the heat pump changes operating modes. In this way, a sum of output of controllers providing output for a new heat pump operating mode may match or equal a sum of output of controllers supplying commands for a different heat pump operating mode so that a heat pump compressor speed is not substantially changed during a transition or change from one heat pump mode to a next heat pump mode.
The present description may provide several advantages. Specifically, the approach may improve heat pump mode transitions. Additionally, the approach may improve heat pump durability. Further, the approach may reduce objectionable noise of a vehicle that includes a heat pump.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.